An exemplary conventional induction heating cooker will be described with reference to the drawings (for example, see Japanese Unexamined Patent Publication No. 2001-196153). FIG. 17A is a plan view showing a state where a conventional induction heating cooker is installed in a cabinet of a kitchen unit, and FIG. 17B is a cross-sectional view taken along line A-A in FIG. 17A. FIG. 18 is a perspective view showing the schematic structure of the conventional induction heating cooker.
As shown in FIG. 17A, the conventional induction heating cooker includes a flat plate 201 structured with a nonmetallic member such as heat resistant glass, and a container portion 208 disposed below the plate 201.
Disposed in the container portion 208 are heating coils 221, 222, and 223 that inductively heat a heating-target object, such as a cooking vessel, placed on the plate 201. It is noted that some conventional induction heating cookers have any of the heating coils 221, 222, and 223 replaced by electric heaters, e.g., radiant heaters, which resistively heat the heating-target object. The heating coils 221, 222, and 223 are disposed, for example, to leave about 5 mm of space to the back surface of the plate 201. Viewing the bottom side of FIG. 17A as the front side (near side) and the top side of FIG. 17A as the rear side (far side), the heating coil 221 is disposed on the front left side, the heating coil 222 being disposed on the front right side, and the heating coil 223 being disposed at the rear center.
In the container portion 208, a roaster 206 for grilling a food such as a fish is disposed below the front-left side heating coil 221. In the roaster 206, an electrical resistance heater, a grid, a drip pan, and the like are disposed. In the container portion 208, an inverter device 205 that supplies high frequency electric power to each of the heating coils 221 and 222 is disposed on the right side of the roaster 206. In the inverter device 205, an inverter circuit board that corresponds to the heating coil 221 and an inverter circuit board corresponding to the heating coil 222 are disposed in parallel one above the other.
As shown in FIG. 17A, the induction heating cooker structured as above is installed in a kitchen unit by having its container portion 208 inserted into an opening 212 provided at a top board 220 of a cabinet 209 of the kitchen unit, with the outer circumferential portion of its plate 201 being placed on a top board 220.
It is noted herein that the opening 212 of the kitchen unit is previously provided at the top board 220 in order to facilitate installation of various heating cooker devices, such as induction heating cookers, gas stove devices, and the like, in the cabinet 209. The manufacturers of the kitchen units employ a substantially unified size of the opening 212. For example, Japanese manufacturers of the kitchen units set the lateral width of the opening 212 to about 560 mm. Consequently, the outer casings of various heating cooker devices also have their external dimensions substantially unified. This eliminates the need for caring about discrepancy in various dimensions between the kitchen units and the heating cooker devices when newly purchasing the heating cooker devices as replacements, which are shorter in product lifetime than the kitchen units, thereby enhancing flexibility in choosing the heating cooker devices.
However, with the conventional induction heating cookers, the size of the container portion 208 is determined by the size of the opening 212 of the kitchen unit. Therefore, the size, layout, and the like of the heating coils 221, 222, and 223 disposed in the container portion 208 are restricted. That is, with the conventional induction heating cookers, it is difficult to increase the diameter of each of the heating coils 221, 222, and 223. For example, when the container portion 208 is designed to have the same lateral width as that of the opening 212, the diameter of each of the heating coils 221 and 222 disposed in the container portion 208 will be at a maximum of 280 mm (=560 mm/2). In this case, with a cooking vessel whose bottom diameter is more than 280 mm, it is difficult to heat the cooking vessel with an excellent heat distribution, i.e., to uniformly heat the entire bottom of the cooking vessel.
Further, as to cooking vessels such as frying pans, their diameter measured at any midway portions of the height other than at the bottom is usually greater than the diameter at the bottom. For example, when the diameter at the bottom is 260 mm, the diameter measured at the midway portions of the height is generally 300 mm or more. Accordingly, for example, when placing one cooking vessel on the heating coil 221 and the other cooking vessel on the heating coil 222 in order to heat the two cooking vessels simultaneously, care must be taken to avoid contact between respective sides of the cooking vessels. Additionally, since the cooking vessels are each usually provided with a handle, care must also be taken to avoid contact between the handle of one of the cooking vessels and the other cooking vessel. Therefore, when two cooking vessels each having a great bottom diameter are heated simultaneously, it becomes difficult to align the center of each heating coil and the center of each cooking vessel, and hence it becomes difficult to uniformly heat the entire bottom of each cooking vessel. Accordingly, the conventional induction heating cookers have need, e.g., to separately heat two cooking vessels of great bottom diameters, thereby posing an issue of insufficient cooking work efficiency.
Still further, in the conventional induction heating cookers, in order to dispose a plurality of heating coils each of whose diameter is as maximized as possible under the condition that the size of the container portion 208 is determined, the heating coils 221 and 222 and the heating coil 223 are disposed as being displaced on the front side and on the rear side, respectively. In this case, there arises an issue that the rear heating coil 223 is awkward to use, particularly when cooking vessels are heated by the front heating coils 221 and 222.
Still further, as shown in FIG. 19, when a ring-shaped magnetic field shielding member 217 is disposed around the outer circumference of each of the heating coils 221, 222, and 223 so as to suppress magnetic field leakage from the heating coils, there arises an issue that the size of each of the heating coils must further be reduced.
Accordingly, an object of the present invention is to solve the issues described above, and to provide an induction heating cooker and a kitchen unit provided with the cooker, with which the size of heating coils can freely be set without being restricted by the size of an opening of a cabinet of a kitchen unit.